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Symptoms & history;
It used oil (approx. 1 qt. per 2-3 tanks) and I read the history of V8 valve stem problems (internet & local shop research), I was about to have the valve guide/stem seals replaced or drive the car off a cliff. But it didn’t have the classic symptoms of defective valve stem seals/guides. It also ran like a rapped ape (old school for ran great). I’m a heavy truck mechanic with old school car experience (35 years). The plugs were clean and the exhaust smelled funny, also the exhaust dripped clean water no matter how hot or long it ran. I pulled the intake throttle housing and noticed excessive oil. Replaced the (ccv) diaphragms in the valve covers (torn) & read up on the cyclone oil separator (like a Dyson vacuum). Because I wasn’t happy with the oil consumption & residue in the intake, I fabricated a sponge with screen for each valve cover vent outlet. This cleaned out the oil residue and I assume it will reduce oil consumption while allowing crankcase recirculation, but it did not solve the smoke problem. I pulled the spark plugs and stuck a camera down a couple plug holes. Yes, the top of the pistons were loaded with carbon. So I sprayed Sea Foam in each plug hole, followed by a shot of low pressure shop air to help spread it around the piston. I let it sit for an hour or so, then reinstalled the plugs. I topped off the fuel tank with high octane and added 12 oz. of CRC Fuel System Cleaner (part #05063) to the tank. 100 miles later and what a difference – no smoke or water dipping out the exhaust after warm up. I’m in love with the car again

**The valve stem diameter was increase at a production point (you would assume) to remedy the guide problem. I could't believe BMW would continue to use inferior stem seals after this change. My vehicle has now passed smog test & no longer smokes. I did have to run the proceedure twice before it lowerd the HC levels within specs. And I will probably do it 1 more time for good measure. It cost me $200 to fix compared to the $4000 > $5000 I was told it would take for a guide/seal replacement **

**** Day 14 - 760 miles later NO smoke or excessive water from tailpipe - It also **** Does not need any oil ****
For those of you seasoned mechanics replacing guides & seals - This worked for me - my vehicle - my situation - but I believe you should diagnose each vehicle on an individual basis - Regardless of BMW guide/valve stem history.

**Note: I need to give full credit to my 25 yr. old friend/mechanic/smog tech/neighbor for his insistence I try Sea Foam. He works on BMWs, Mercedes and other makes. I never heard of Sea Foam (we used Justice Brothers in my hay day) and I didn't believe it would solve my issue. Although it was my idea to soak the piston tops first before spraying it thru the intake. I'll also take credit for the sponge/foam/screen in the PCV hose idea. **

I first heard about seafoam recently as well. My 03 745li was running rough and smoked if you let it sit a few days without running it. I bought a few cans of seafoam and since I couldnt find which vacuum to use to get it in the intake I decided to run the car tilll heated to opperating temps, disconnected the air filter leaving the maf and while running I slowly dumped the seafoam into the intake fast enought to get it in all cylinders but not too fast that it stalled the engine and also not to hydrolock the motor which is detrimental. anyways I dumped a can in the gas tank same time while it was damn near empty and once I got most of the can in the intake I shut off the car and waited about 15 minutes or so. then I restarted the car and ran it till the smoke died down ( It will completely engolf your neighborhood with smoke ) LOL anyways I ran it to the gas station and filled up and by the time I got back home the smoke was gone, hasnt smoked since and idles and runs smooth and even if sitting a week or more does not smoke on startup.

In addition, the seafoam worked to well I plan to use it my next oil change. I will drain about a quart of oil then add a quart of seafoam and run the engine for about 15 minutes or so reving once in a while as not to let it idle too long, then change the oil. Im told this will clean carbon throughout the motor and free up lifters clean oil holes etc.

sorry jsut realised I hyjacked your thread. to answer your question I just went out to my 7 and started it up and removed the oil cap. there was a definite vacuum which made it hard to pull the cap off but once I did it stayed running the idle was rough but stayed running. hope that helps.

The correct proportion is 1.5 ounces per quart of oil. The N62 takes 8.5 quarts and the N73 takes 9. So you should only mix 12 - 13.5 ounces of seafoam in your oil. And some people say that's too much. Just don't run it for more than a few miles.

In addition, the seafoam worked to well I plan to use it my next oil change. I will drain about a quart of oil then add a quart of seafoam and run the engine for about 15 minutes or so reving once in a while as not to let it idle too long, then change the oil. Im told this will clean carbon throughout the motor and free up lifters clean oil holes etc.

It's great to here Sea Foam worked for you. Although I would be hesitant to add any additive to my oil. Here's an update on my vehicle:
**** Day 65 +/- 2500 miles later NO smoke from tailpipe - It also only used maybe a qt. oil **** I changed to a 5w-40 synthetic and will do every 7,000 miles - I'm also adding 12oz. Techron Concentrate Plus every 2-3 tanks to combat the existing carbon (for now).
*updated 8/27/13*